To suppress vibration of the distal end of a multi-link robotic arm, it is necessary to estimate the axial torsional angular velocity (the difference between the link angular velocity and the motor angular velocity) based on the motor angular velocity, measured by an internal motor encoder which drives each shaft, and feed it back to a motor angular velocity control system. This estimation operation requires an observer based on a nonlinear dynamic model that takes into consideration elastic joints, and nonlinear interference forces acting between the links.
Attainment of a multi-input multi-output nonlinear observer as described above requires creation of an accurate dynamic model, and a given robustness against variations in end effector load/frictional force. Conventionally, an approximate observer based on one-input one-output linear model+α for “Elastic Joint Model for Each Link+Disturbance Estimation and Compensation from Other Links” has mainly been used to reduce the amount of computation of control.
Also, with the recent improvements in performance of a CPU and memory, a robotic control apparatus can also achieve various computing powers and storage capacities.